Polyamide composition and process for preparing the same



"out'tlie "u'se'of solvents, for example, by

Unite States Patent rbLYAa iIDncoMrosIrro success FOR *rnnranmo "rnnsAMn "Arthur B'. Beindortf, Decatur, Ala, assignor' to The *Ghemstrandflorporation, Decatur, Ala., a corporation of Delaware s re mlining. =a lmen ssameness, -"Serial No. 517g041 140mm. '(ci. 260 30.43

Thisihventionf'relates to new" compositions or matter "ep'a'rticularly, tonew compositions of "rriatter ngsymheiic' linear" polyamides and to methods of p ing the saine. Syrlfliitic linearpol anndes are genericall referred 't' nylon. Although "the polyamidesas a 'class-"are ocry'sta1l'ineandhave fairly 'high"andsliarp melting oints, they can be" formed into annivns l"-'objects with "extruding the 'molten"polyarnide"through a spinner'etoreldngat'ed slit to form filaments or films. Howeverfsolutions of the polyarnidesfa're"likewise useful and in manyapplications "areas-ore advantageousthan molten compositions, such as to'achievethefluid state necessary inlacqiierscoating "cori'ipos'itions, and the like. Further, solutions dfthe polyamides can be weespun "into "various snapedand useful articles, such as films, fibers, filaments, rods, tapes, tubes, bristles, ribbons, sheets, etc. Very often it is dcsirabl'e to prepare afiuidcomposition for useovera period =f time an in that event it 'is convenient in the -composi- "tidn can-be kepfin the'liquid stage by storage at'ordinary temperatures.

rnman "applications it 'is "necessary 'to incorporate additives in 'thepolyamides, such as plasticizers orother *n'iodifying agents. Such addition is more advantageously accomplished byincorporating the additive in a-solution ofthe Jpolyamide' rather '-thanin the molten polyamide. Fr'equently'Qwh-ensuch blending is done" in amelt, there is a'tendencytoWard discoloration and decomposition of the polymer. Further, there is a'tendency with-certain types of plasticizers and modifying agents to be less compatible at the high temperatures required for blend- -ingin amelt, whereas they can be readily incorporated 'in a'polyainide solution at'a lowftempera ture. 'In addi- "tion, solutions of polyamides are more easily cast'into coatingsof uniform thickness, which is mechanically more difficult 'to accomplish with a molten composition due to its relatively high viscosity. c 4 'Many solvents'forpolyamides, as defined herein, have i eretofore been proposed but most'of these solvents are lacking in one or, more particulars. The, polyamides as "a class characteristically require corrosive media as solvents, such as strong concentrated acids, phenols, cresols, and thelike, particularly where solutions'of the "polyamides having useful degrees of concentration are required. Furthermore, and particularly whenstro'ng acids 'are'u'sedas solvents, degradation'of thepolyainideconsutures a'serious obstacle,'especially at higher temperatures and concentrations, and this is so even when phenolic "solventsjar'e 'employed. v c 7 Accordingly, it is'a primary object of the present inmention to overcome the aforementioned disadvantages and-provide a new and useful solvent for synthetic linear polyamides. It is another object of the invention to "provide "a new and useful composition of matter comprising a syntheticlinea'r polyamide solution which "can 'beform'ed ihtoshaped articles, such as threads, filaments, fibers,"ribbons, rods,-brist1e's, tapes, tubes,'films, andthe 71311205: (I? O\ N-C-CH:

CHsCfi:

Theteinperature atwhich solution of the polyamide takes-place will vary with the composition of the polyamideaudits viscosity or molecular weight. Generally, however, temperatures in the range of 150 C. to 190 C.'are suflieient toeftect solutionof the syntheticlinear wpolyamides in N-acetyl morpholine.

The polyamides which-are useful in the practice of the :fpresent-inventi0n;are;0f the general types described'in U. S. Patents2,071,250, 2,071,253 and 2,130,948. Accordingly, throughout the'instant specification and claims,

the terms syntheticlinear-polyamides and polyamides designate the general types described in said patents.

A characteristicproperty of these polyamides or poly- 'mersfis that they can be formedinto filaments which can be cold drawn into fibers showing molecular orientation along the fiber axis. The polyamides are particularly usefulfor thepreparation of fibers, bristles, sheets, rods, tubes, and the like. The polyamides are of two types, those obtainable from polymerizable monoaminomonocarboxylic acids and their amide-forming derivatives, for

example, caprolactam, and those obtainable from the reaction of'suitable diamines and suitable dicarboxylic acids or amide-forming derivatives of dibasic dicarboxylic acids. In th'ese polyamides the amide group forms aninteg ral part of themain chain of atoms in the polymer. On

hydrolysis with strong mineral-acids, thepolya mide s revert to monomeric polyamide forming reactants. "The polyamides may also be'defined as long-chain synthetic polymeric carbonamides which have recurring carbon- 'amide-groups as an integral part of the 'main polynier chainfiand which are capable of being formed into a filament, this definition being patterned rather closely after Wakernan, The Chemistry of Commercial Plastics, Reinhold Publishing Company, 1947, page 257. In accordance with the present invention, solutions or dupes containing'from 5 to 25% by weight of polyamide are suitable for the formation of filaments and fibers. The concentration of the-polyamides which can be obtained in solution and the viscosity of the solution depend upon the nature of the polymer, the solvent employed and-the temperature. Usually, when making a solution of a polyamidewhichis to be employed in the manufacture of fibers and filaments, a polyamide having an intrinsic viscosity 0t 0 .3 to 2.0 orabove is employed. For ex- -ample,-as much as 20-25% by weight of polyhexamethylc0 eneadiparnide having an intrinsic viscosity of about 0.36 can be dissolved in glutaricacid at 98 C. Polyamides having alower. molecular weight or intrinsic viscosity are employed when the solution or dope is to be used for coating or as alacquer. While it is preferred teem- 5 ploy 5 to 25% by weightof the polyami de in the solutions when the solution is'to be used in forming fibers and filaments, it is to be understood that less than 5% -or more than 25% p olyamide may be used when the solution is to be employed for other purposes, such as coating,

or in lacquers, and the like, or whenlow molecular weight polyamides are employed. The amount of any specific =polyamide, which can be dissolved in the solvent Offl-N '3 present invention, will be readily evident to those skilled in the art.

Generally, heating of the solutions is accomplished on a water or oil bath. However, other means maybe employed, if desired. Agitation of the mixture during the heating process is preferred but it should be understood that agitation is not always necessary nor critical. Agitation can be accomplished by any suitable means, such as by stirring, shaking, etc.

While each polymer varies somewhat in its solubility characteristics and the temperature of solvation, this invention is applicable to all synthetic linear polyamides, as hereinbefore defined. As indicated, the polyamides are generally of two types, those derived from polymerizable monoaminomonocarboxylic acids or their amide-forming derivatives, and those derived from the reaction of suitable diamines with suitable dicarboxylic acids or amideforming derivatives of dicarboxylic acids. On hydrolysis with mineral acids, the polyamides yield monomeric polyamide-forming reactants. For example, a polyamide derived from a diamine and a dibasic acid yields on bydrolysis with hydrochloric acid, the dibasic acid and the diamine hydrochloride. Similarly, an aminoacid type polyamide yields an aminoacid hydrochloride. Particularly useful polyamides in the present invention are the simple unsubstituted polyamides, such as those formed by the reaction of tetramethylene diamine with adipic acid, tetramethylene diamine with suberic acid, tetramethylene diamine with sebacic acid, hexamethylene diamine with adipic acid, hexamethylene diamine with suberic acid, hexamethylene diamine with sebacic acid, the polymerization products of epsilon-caprolactam, etc. In addition, polymers formed from the reaction of two or more diamines with dicarboxylic acids and/or two or more dicarboxylic acids with diamines are contemplated in the practice of the instant invention. These polymers all dissolve in N-acetyl morpholine in accordance with the present invention as to do the inter-polymers which are normally insoluble in most simple alcohols.

The most useful polyamides are the higher molecular weight polyamides, that is, those having an intrinsic viscosity of 0.3 or above, since they possess the property of being formed into filaments which can be cold-drawn. That is, filaments produced from the present polyamide compositions have the ability to accept a very high degree of permanent orientation under stress. By the application of moderate stress at ordinary temperatures these filaments can be instantly elongated or cold-drawn. The filaments can be cold-drawn as much as several times their original lengths. The cold-drawing operations may be carried out on filaments, which have been allowed to cool fully and solidify, or the cold-drawing may follow the formation of the filaments directly as one part of a continuous process. The filaments, which are cold-drawn, possess a high degree of permanent orientation along the filaments axis, as shown by characteristic X-ray patterns. These high molecular weight varieties of the polyamides are more useful for most purposes than the lower molecular weight polyamides since they excel in toughness and durability.

The polyamide compositions of the instant invention are particularly useful for the formation of shaped articles by the so-called wet-spinning technique wherein a solution or dope of the polyamide is extruded through a suitably shaped orifice into a bath comprising a nonsolvent for the polyamide. It is particularly desirable to employ the wet-spinning technique, if at all possible, and the present invention provides the means of wetspinning polyamide structures. The wet-spinning method has a number of advantages over the melt-spinning technique, which is presently widely used, for example, the wet-spinning method is generally more economical and can be operated at lower temperatures than melt-spinning. Because of the lower temperatures, plasticizers and other modifying agents can be more advantageously added to 4 l a solution rather than to a molten polyamide, thereby minimizing the tendency toward discoloration and decomposition. Further, there is a tendency with certain types of plasticizers and modifying agents to be less compatible at the high temperatures required for blending in a melt, whereas they can be readily incorporated in a polyamide solution at a low temperature. A still further advantage in the use of solutions lies in the ease with which they can be cast into films or coatings of uniform thickness, which is mechanically more difficult to accomplish with a molten composition due to its relatively high viscosity.

While the wet-spinning technique for forming shaped articles from polyamides is preferred, as pointed out above, it has not been employed commercially due to the scarcity of suitable solvents, since polyamides are generally insoluble in most of the well-known organic solvents. Therefore, the present invention is advantageous in that it answers a serious need which has existed for the discovery of a suitable solvent for the wet-spinning of polyamide shaped articles and one which provides polyamide solutions of suitable concentration and stability which can be prepared conveniently with standard equipment. In addition, the solvent of the present invention can readily and conveniently be recovered for reuse or re-cyling during the employment of the polyamide solutions for transforming the polyamide into other forms, such as filaments, fibers, films, and the like.

For a more detailed description of the present invention, reference is had to the following specific examples which are merely intended to be illustrative and not limitative. In the examples, all parts and percent are by weight unless otherwise indicated.

Example 1 One part of polycaprolactam and 3 parts of N-acetyl morpholine were mixed in a tube and heated to a temperature of 170 C. The polymer dissolved readily giving a clear, homogeneous solution which was fiuid. Upon heating the polymer solution to the boil (240 C.), discoloration was observed. The solution coagulated immediately when introduced into a bath of N,N-dimethylacetamide. Strong films were formed when the polycaprolactam solution was extruded into a bath containing 50% N-acetyl morpholine and 50% N,N-dimethylacetamide. 'Ihe polycaprolactam solution was coagulated in water.

Example 11 Ten parts of polyhexamethylene adipamide and parts of N-acetyl morpholine were mixed in a tube and heated to a temperature of C. to C. The polyamide began to dissolve at 150 C. and solution was complete upon reaching C. The solution obtained was clear, homogeneous and non-viscous. Good films were obtained by extruding the polymer solution or "dope" into water. Films were also obtained in baths of 50/50 water/N,N-dimethylacetamide and water/N-acetyl morpholine.

In addition to use in wet-spinning, the polyamide solutions or compositions of this invention may be employed in dry-spinning wherein the solution or dope is extruded through a suitably shaped orifice into a heated atmosphere capable of evaporating the solvent from the newly formed article.

The properties of the objects formed from the polyamide compositions herein described may be modified by appropriate modification of the compositions. Thus, the compositions of this invention may have incorporated therein various modifying agents, such as plasticizers, dyes, pigments, diluents, resins, cellulose derivatives, waxes, water repellants, luster modifying agents, flame repellants, and the like. Solutions of different polyamides, or of polyamides with other polymers or solutes canbe solution blended and precipitated to give homogeneous blends, where melt blending is undesirable or impractical.

In addition to the formation of filaments, fibers, films, etc., the instant polyamide compositions can be formed into a variety of other objects, for example, bristles, surgical sutures, fishing leaders, fishline, dental floss, ribbons, sheets, safety glass inner layers, golf ball covers, and plasticized or otherwise modified solid compositions useful for making molded articles. The instant polyamide compositions are also useful for coating wire, fabrics, paper, regenerated cellulose, and the like, and for impregnating fabric, paper, and other porous materials. Numerous other advantages of the instant invention will be apparent to those skilled in the art.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

I claim:

1. As a new composition of matter a clear, homogeneous solution comprising a synthetic linear polyamide and N-acetyl morpholine, said polyamide being a long-chain synthetic polymeric carbonamide which has recurring carbonamide groups as an integral part of the main polymer chain and which is capable of being formed into afilament.

2. A composition of matter as defined in claim 1 wherein the polyamide is polycaprolactam.

3. A composition of matter as defined in claim 1 wherein the polyamide is polyhexamethylene adipamide.

4. A composition of matter as defined in claim 1 wherein the polyamide is polyhexamethylene sebacamide.

5. A composition of matter as defined in claim .1 wherein the polyamide is polytetramethylene adipamide.

6. A composition of matter as defined in claim 1 wherein the polyamide is polytetramethylene sebacamide.

7. A process for preparing a new composition of matter comprising mixing a synthetic linear polyamide with N-acetyl morpholine and heating said mixture to a tem perature in the range of C. to 190 C. to form a clear, homogeneous solution, said polyamide being a longchain synthetic polymeric carbonamide which has recurring carbonamide groups as an integral part of the main polymer chain and which is capable of being formed into a filament.

8. The process as defined in claim 7 wherein the polyamide is polycaprolactam.

9. The process as defined in claim 7 wherein the polyamide is polyhexamethylene adipamide.

10. The process as defined in claim 7 wherein the polyamide is polyhexamethylene sebacamide.

11. The process as defined in claim 7 wherein the polyamide is polytetramethylene adipamide.

12. The process as defined in claim 7 wherein the polyamide is polytetramethylene sebacamide.

13. A process for preparing a new fiber-forming composition of matter comprising mixing a synthetic linear polyamide having an intrinsic viscosity in the range of 0.3 to 2.0 with N-acetyl morpholine, and heating said mixture to a temperature in the range of 150 C. to 190 C. to form a clear, homogeneous solution, said polyamide being employed in sufficient amount to give a solution containing from 5 to 25% by weight of the polyamide, said polyamide being a long-chain synthetic polymeric carbonamide which has recurring carbonamide groups as an integral part of the main polymer chain and which is capable of being formed into a filament.

14. As a new composition of matter, a fiber-forming solution comprising a synthetic linear polyamide having an intrinsic viscosity from 0.3 to 2.0 and N-acetyl morpholine, said polyamide being a long-chain synthetic polymeric carbonamide which has recurring carbonamide groups as an integral part of the main polymer chain and which is capable of being formed into a filament.

No references cited. 

1. AS A NEW COMPOSITION OF MATTER A CLEAR HOMOGENEOUS SOLUTION COMPRISING A SYNTHETIC LINEAR POLYAMIDE AND N-ACETYL MORPHOLINE, SAID POLYAMIDE BEING A LONG-CHAIN SYNETHIC POLYMERIC CARBONAMIDE WHICH HAS RECURRING CARBONAMIDE GROUPS AS AN INTEGRAL PART OF THE MAIN POLYMER CHAIN AND WHICH IS CAPABLE OF BEING FORMED INTO A FILAMENT. 